When people witness some incident, such as a crime or accident, they may subsequently be exposed to new information about that incident. Our past work has shown that such new information, whether true or false, can become integrated into memory and thereby alter recollection. The current proposal is in part an extension of this past work with the major goal of exploring the nature of the integraion process. The work is guided by two basic principles that constitute the beginning of a framework for discussing when and how changes in recollection occur. These two principles are: (1) Change in memory for an event is more likely to occur if discrepancies between the original and post-event information are not initially detected at the time the post-event information is processed. (2) Change in memory for an event is completed by the act of recollection. These principles are explored in a series of studies in which subject-witnesses first view videotapes or slides depicting complex events. Later they are tested. Prior to testing, some subjects are exposed to new information, and the extent to which subjects incorporate this information into memory is measured. Additionally, one line of experimentation is designed to ascertain whether there is any way to distinguish a memory that results from a true perceptual experience and one that results from post-event suggestion.